Just a thought, If the tank was not venting, you should experience a problem when fueling (filling up). The air in the tank must be displaced as the tank fills, which would not be possible with a plugged vent. My guess is an obstruction inside the tank, or checkvalve, or collasped fuel line...
Good info guys. I have the same problem with my Suzuki DF225, 4 stroke. Runs and idles great, up to about 6 MPH. Then primer bulb collapses. Changed in-line (spin on) filter repeatedly. Also changed the primer bulb. Tested a fuel sample for water and/or trash at the primer bulb discharge, and...
